GB2179555A

GB2179555A - X-ray transmissive electrode for a living body

Info

Publication number: GB2179555A
Application number: GB08620697A
Authority: GB
Inventors: Masatomo Shigeta; Hikonori Abe; Shinichi Nishiyama
Original assignee: Kureha Corp
Current assignee: Kureha Corp
Priority date: 1985-08-27
Filing date: 1986-08-27
Publication date: 1987-03-11
Also published as: DE3628652A1; US4748983A; FR2586570A1; GB2179555B; GB8620697D0; DE3628652C2

Description

1 GB' 2 179 555 A 1

SPECIFICATION

X-ray transmissive electrode for a living body.

The present invention relates to an electrode suitable for application to a living body and which can be used as the electrode of, for example, a difibrillator or an electrocardiograph and the like.

When carrying out catheter-inspection of a patient's heart, a catheter is inserted into a blood vessel and X-ray photography is carried out after introducing a contrast media into the heart via the blood vessel.

In some patients this causes excitement and this can cause cardiac convulsion for longer than 15 to 30 sec during the inspection. Prolonged cardiac convulsion leads to stagnation of the blood,thereby causing damage to the cerebral cells. Frequently a high voltage shock of 3000 to 5000 V has to be given to the heart of the patient while using a difibrillator, in order to prevent this damage.

The conventional defibrillator has the shape of a box provided with a handle on its upper part and an electrode on its lower surface. The electric shock is given by pressing the electrode onto the patient in the region of the heart. However the conventional defibrillator generally can only be applied to the patient afterthe cardiac convulsion has occurred as its prior application may interfere with or prevent the treatment or inspection of the patient. The use of the conventional defibrillator is therefore inconvenient and there is a risk of dangerous delay in meeting an emergency.

In some cases an electrode has been preliminarly adhered to the surface of the body of the patient, for instance due to the necessity of taking electrocardiogram during X-ray photographing. However, since the conventional electrode is made of a metal and does not transmit X-rays, such an electrode has been an obstacle to the X-ray photography.

It would be desirable to be able to use an electrode that is transparent to X-rays.

An electrode according to the present invention for a living body comprises an electrode substrate comprising a porous material composed of granular 110 or fibrous carbon and is substantially transparent to X-rays, and the pores in the electrode substrate are impregnated with an electrolyte. The electrode should normally be flexible and preferably the electrode substrate comprises flexible and porous 115 material.

In the accompanying drawings; Figures 1A and 1 B each show a vertical section of an electrode of a defibrillator according to the present invention, and more in detail; Figures 2A and 213 are respectively the side view of the plane figure of a main part of the electrode substrate of a defibrillator in use; Figure 3A is an analytical oblique view showing the junction of the electrode and the lead part according to one of the examples of the present invention; Figure 3B is an analytical oblique view showing the junction of the electrode and the lead part according to another example of the present 130 invention; Figure 4 shows the vertical section of the electrode according to another example of the present invention and Figure 5 is an oblique view showing the flexibility of the flexible sheet.

The electrode substrate can be of granular or fibrous carbon, as in Figure 1A, in which event it need not be flexible but preferably it is of fibrous carbon and is flexible, as in Figure 1 B. The defibrillator consists of the high pressuregenerating part 1, a pair of electrodes 2 and the lead part 3 which connects the above mentioned parts, and each of the electrodes 2 is installed on the heart region of the patient 4 from the breast side and the back side. Each electrode is directly adhered to the skin of the patient by a suitable adhesive and is further fixed by a band 5. It is necessary that the electrode of the defibrillator is fixed firmly because the shock of the high voltage is otherwise likely to make the electrode come off the patient.

Each electrode 2 comprises an electrode substrate 20 which consists of a disk-like porous carbonaceous material typically of about 50 cm' in area and 0.1 to 1 mm in thickness. A ring-form sponge 7 may be provided for covering the disc and 8 is a protective membrane 8 may be provided on the upper surface of the electrode substrate 20.

The thickness t of the electrode substrate 20 is preferably not more than 10 mm (as otherwise it can be uncomfortable to the patient) and more preferably not more than 2 mm.

Furthermore, particularly in the case of the defibrillator, since a large current is applied under a high voltage of 3000 to 5000 V, the electrical resistance of the electrode substrate 20 is preferably not more than 1.0 Q. In the case where the resistance is too high, there is fear of burns due to the generation of heat in the electrode.

A flexible porous electrode substrate 20 (as in Figure 1 B) may comprise a sheet-like porous material produced by (1) manufacturing an original sheet-like material from relatively long carbon fibres of not less than 3 mm in length by papermanufacturing method, (2) impregnating the thus manufactured original sheet-like material with a thermosetting resin such as phenol resin, epoxy resin, etc. thereby binding the carbon fibres to each other and (3) carbonizing the thus impregnated material by calcining thereof under a reduced pressure or in an inert gas atmosphere. The porous electrode substrate 20 includes a number of pores preferably of a diameter of about 80 to 120 lim. The pores have been impregnated with an electrolyte solution that is preferably a jelly-like electrolyte solution such as physiological saline solution.

Alternatively, the porous electrode substrate 20 may be constituted of a carbonaceous mould substrate plate scarcely showing flexibility, as in Figure 1 B. Such a mould substrate plate can be obtained by (1) mixing fibrous carbon of not more than 3 mm in length or granular carbon of not more than 1 mm in diameter with particles of thermosetting resin such as phenol resin, epoxy resin, etc., (2) moulding the 2 GB 2 179 555 A 2 thus prepared mixture, for instance, at temperature of 140 to 1500C under a pressure of 50 kg/cm'G and then (3) calcining and carbonizing the thus moulded material under a reduced pressure or in an inert gas atmosphere at a temperature of not less than 70 15000C.

The thus obtained mould substrate plate may contain substantially uniformly pores of 20 to 80 pm in diameter and have a porosity of 40 to 90%.

Accordingly, when these pores are impregnated with the electrolyte solution such as physiological saline solution, etc., the contact surface area between the pore and the electrolyte solution is 2 times as large as that in the above-mentioned example of the porous sheet-like material. 80 The flexible electrode substrate 20 is preferably composed of a flexible and porous carbonaceous material produced by (1) preliminarily subjecting relatively long carbon fibres of not less than 1 mm in length to heat treatment at a temperature of not less 85 than 15000C, more preferably not less than 2000'C, (2) manufacturing the thus treated carbon fibres into an original paper sheet-like material by a paper manufacturing method, (3) impregnating the thus obtained paper sheet-like material with a thermosetting resin such as phenol resin, epoxy resin, as a binding agent, thereby binding the carbon filaments to each other and then (4) calcining and carbonizing the thus impregnated material under a reduced pressure or in an inert gas atmosphere. The thus produced flexible electrode substrate 20 generally has pores of 20 to 120 pm in diameter formed nearly uniformly and a porosity of to 90%, and the pores have been impregnated with a jelly-like electrolyte solution such as physiological saline solution. Suitable material, and its manufacture, is described in more detail in our application reference 6012611101 filed even date herewith.

Before manufacturing the paper sheet-like 105 material used for producing the flexible electrode substrate from the carbon fibres, it is generally necessary to previously subject the carbon filaments to high temperature treatment for inactivating the surface of the carbon fibres. The reason is as follows:

Within the flexible electrode substrate 20 after being carbonized, a number of mutually intersecting carbon fibres are restrained on each of the intersecting points by the carbon lumps derived 115 from the binding agent. In such a situation, when the surface of the carbon fibres is made to be inactive, the carbon fibres and the carbon lump derived from the binding agent freely slide to each other and accordingly, a moderate flexibility is given 120 to the electrode substrate on the whole.

In addition, in the case where carbon fibres initially sheafed by a sheafing agent are used, the sheafing agent should be removed by washing with a solvent such as acetone and the thus washed carbon fibres are subjected to heat-treatment at a high temperature to inactivate the surface of the carbon fibres.

The flexibility of the flexible electrode substrate 20 is preferably so that, as is shown in Fig. 5, the 130 flexible and porous carbon material 6 constituting the electrode substrate has a ratio D/d, wherein D is the diameter of the curvature just before the breakage of the material 6 when it is bent until the breakage (the minimum diameter of the curvature) and d is the thickness of the material 6, of not more than 200. In the case where the ratio D/d is over 200, the necessary flexibility is not available and since the following-up property and the close adhesiveness to the living body are reduced, the electrode is liable to come off from the living body due to the high voltage shock.

In order to improve the affinity and adhesiveness of the electrode substrate to the living body and to improve the buffering property thereof to the high voltage shock, a buffering material 21 such as a sponge, often impregnated with, for instance, a physiological saline solution is usually provided between the porous electrode substrate 20 and the living body as seen from Figures 1A and 1 B. The lead part 3 of the defibrillator is preferably composed of a flexible graphite sheet while particularly being located in the vicinity of the electrode 2.

Such a flexible graphite sheet may be produced by high pressure moulding of the expanded graphite particles obtained by treating graphite particles with 98% concentrated suffuric acid, for instance, it may be GRAFOIL (trade mark) made by Union Carbide Corporation.

An example of the lead part 3 composed of GRAFOIL is shown in Figure 3A.

Since GRAFOIL may be moulded into any desired form by cold punching, it is very suitable for mass production and gives good results as the contact resistance between the lead part 3 and the electrode substrate 20 can be reduced to a negligible extent.

The adhesion of the electrode substrate 20 to the lead part 3 can be achieved using an electroconductive adhesive prepared by admixing microparticles of carbon such as carbon black with a thermosetting resin, e.g., a phenol resin or epoxy resin. The amount of micro-particles of carbon admixed is preferably 30 to 90% by weight of the mixture. If the amount is below 30% by weight, the necessary electroconductivity may not be obtainable, and if the amount is over 90% by weight, the adhesive strength may be too low.

Another electroconductive adhesive can be a mixture prepared by admixing micro-particles of carbon such as carbon black with a rubber-like resin such as natural crude rubber orthe synthetic crude rubber. Again the amount of micro-particles of carbon admixed is preferably 30 to 90% by weight of the mixture for the same reasons as above. Although this adhesive gives lower adhesive strength it is able to provide a flexible joint.

In another method, the electrode substrate 20 and the lead part 3 are joined together by using an adhesive prepared by admixing micro-particles of carbon such as carbon black with thermosetting resin, and then the joined part is calcined and carbonized under a reduced pressure or in an inert gas atmosphere at a temperature of not less than 1000'C. This leads to a negligible electric resistance.

3 GB 2 179 555 A 3 As the thermosetting resin for use in the above mentioned method, phenol resin, epoxy resin, etc.

may be mentioned. The amount of micro-particles of carbon admixed is preferably not more than 90% by weight of the mixture. In the case where the amount of micro-particles of carbon admixed is too large, there is a fear of reducing the adhesive strength.

In addition, carbon fibres may be used as the lead part 3 but the junction of the lead part and the electrode substrate is less satisfactory due to the increased electric resistance and the great bulk of the lead part. The above mentioned use of a flexible graphite sheet as the lead part 3 avoids this problem.

The electrode 2 including the lead part 3 is substantially transparent to X-rays. Consequently, the electrode does not hinder X-ray photography, and the electrode can be positioned on the living body during X-ray inspection.

Figure 313 shows an example in which the adhesion or the calcining junction of the lead part 3 and the electrode substrate 20 is carried out all over the opposite surface of the electrode substrate 20 to the surface thereof which contacts to the living body. Namely, the above-mentioned example in Fig.

313 is an example in which the shape of the joining surface of the lead part 3 is the same as the shape of the surface of the electrode substrate 20. In such a construction, the joining area is large so that the adhesive strength is large and contact resistance is small.

Fig. 4 shows another example of the present invention. In the example shown in Fig. 4, the electrode is so constructed that a plurality of the electrode substrate blocks 22 are adhered to a flexible graphite sheet 30. By dividing the electrode substrate into a plurality of blocks, the surface of the electrode which faces to the living body has a freely bendable structure even though the substrate of which each block is formed may not be flexible.

However each block 22 may be made of the same material as that of the above-mentioned electrode.

Furthermore, the flexible graphite sheet 30 may also serve the lead part.

Although the electrodes of the invention has been described primarily for use with a defibrillator, the present invention can be applied to the electrodes for an electrocardiograph, and the electrodes according to the present invention can be used as electrodes both in the defibrillator and the electrocardiograph. In addition, the present invention can be applied to the X-ray transmitting type electrode for a living body which is used for measuring electroencephalogram, etc.

Since the electrode substrate has been mainly composed of granular or fibrous carbon thereby making the whole electrode substantiall transparent to X-ray, such an electrode does not hinder X-ray photography even in the case where the electrode is installed on the living body throughout the process. Accordingly, the electrode according to the present invention can be used as the electrode for an electrocardiograph or a defibrillator that is installed throughout the 130 inspection process.

In addition, in the case where the porous and flexible carbon sheet is used as the surface of the electrode which contacts directly to the living body, the contact surface of the electrode is freely bendable. Accordingly, the close adhesion of the electrode to the living body is excellent, and the electrode is not removed due by shocks even in the case when used as the electrode of the defibrillator.

Claims

1. An electrode for a living body having an electrode substrate which comprises a porous material composed of granular or fibrous carbon and which is substantially transparent to X-rays, the pores in the electrode substrate being impregnated with an electrolyte solution.

2. An electrode according to claim 1, wherein the porous material composed of fibrous carbon is flexible. -

3. An electrode according to claim 1 or claim 2, wherein the electrode substrate is provided with a lead part comprising a flexible graphite sheet.

4. An electrode according to claim 3, wherein the lead part is adhered to the electrode substrate by using an electroconductive adhesive prepared by admixing micro-particles of carbor with a thermosetting resin or a rubber-like resin.

5. An electrode according to claim 3, wherein after adhering said lead part to said electrode substrate by using an electroconductive adhesive prepared by admixing micro-particies of carbon with a thermosetting resin, the thus formed bonded part is calcined and joined under a reduced pressure or in an inert gas atmosphere.

6. An electrode according to claim 4 or 5, wherein the calcined and bonded surface between the electrode substrate and the lead part is joined to the total area of surface of the electrode substrate.

7. An electrode according to claim 1, wherein the electrode substrate is made of a plurality of blocks and the blocks are connected mutually by a flexible graphite sheet.

8. An electrode according to any preceding claim, wherein a sponge-like porous buffering material impregnated with an electrolyte solution is provided over the surface of the electrode substrate.

9. An electrode according to claim 1, wherein the electrode substrate comprising a porous and sheet- like material is obtained by (1) manufacturing an original paper-like material from fibrous carbon of not less than 3 mm in length by papermanufacturing method, (2) binding the fibrous carbon mutually by impregnating the thus manufactured original paper-like material with a thermosetting resin and (3) calcining the thus impregnated material under a reduced pressure or in an inert gas atmosphere.

10. An electrode according to claim 1, where said electrode substrate comprising a porous mould substrate plate is obtained by (1) thermally moulding a mixture of fibrous carbon of not more than 3 mm in length of granular carbon of not more than 1 mm in diameter and particles of thermosetting resin and (2) calcining the thus 4 GB 2 179 555 A 4 moulded material under a reduced pressure or in an 25 inert gas atmosphere.

11. An electrode according to claim 10, wherein the electrode substrate substantially uniformly contains pores of 20 to 80 pm in diameter at the porosity of 40 to 90% and the pores are impregnated with the electrolyte solution.

12. An electrolyte according to claim 9 or claim 10, wherein the thermosetting resin is phenol resin or epoxy resin.

13. An electrode according to claim 2, wherein the 35 electrode substrate composed of a flexible and porous carbon material is obtained by (1) manufacturing an original paper sheet-like material from fibrous carbon of not less than 1 mm in length the surface of which is inactivated by preliminary 40 treating at a high temperature, by paper manufacturing method, (2) impregnating the thus obtained original paper sheet-like material with a thermosetting resin, thereby binding the fibrous carbon mutually and then (3) calcining the thus 45 impregnated material under a reduced pressure or in an inert gas atmosphere.

14. An electrode according to claim 13, wherein said fibrous carbon is preliminary subjected to heat treatment at a temperature of not less than 15OWC.

15. An electrode according to claim 13 or claim 14, where a fibrous carbon sheafed by a sheafing agent is washed with a solvent to remove the sheafing agent preliminarily from the fibrous carbon, and the thus washed fibrous carbon is subjected to the heat treatment.

16. An electrode according to claim 13, wherein the thermosetting resin is phenol resin or epoxy resin.

17. An electrode according to claim 13, where the electrode substrate substantially uniformly contains pores of 20 to 120 pm in diameter at a porosity of 40 to 90% and the pores are impregnated with the electrolyte solution.

18. The use of an electrode according to any preceding claim for applying a voltage to a living body.

19. The use according to claim 18 for defibrillation.

20. The use according to claim 18 in which the body is X-rayed through the electrode.

Printed for Her Majesty's Stationery Office by Courier Press, Leamington Spa, 311987. Demand No. 8817356. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.